Welding control system



v FREDERICK ,A. BARNES 9 Jan, 27, 1948. F A, BARNES 2,435,026

WELDING CONTROL SYSTEM Filed June 26, 1944 22 2o 21 Q W %M JQ A.R

PUMP M 3m entor FIG. 7

Patented Jan. 27, 194

UNITED STATES WELiiiNG Frederick A. Bar na Glevel'and nsights, Ohio, as-

signor to Bailey MeterConi pany, rt-corporation of Delaware Application Jarrett, 1944, "Serial 542,209

(oil ern -4a 18 Claims.

This invention relates to control systems,- and particularly to the control-ling of ope-rations in definite relation to time or at a definite rate, for example, so that a, machine partpor the work, moves at a predetermined speed which may be a uniform speed or a-s'p'ee'd varying in "desired relation to time. I

A particular object of my invention is to' 'co ntrol the rate of movement of a movable part of a machine toward or away from a stationary part of the machine at apr-edeterm-ined rate which may be a steady rate or a -s'uccess-ion of difieren't rates. For example, I may establish a sequence of movement rates which thereafter are accomplished automatically.

Hydraulic pressure is used toactu-ate practi cally every type of metal handling or working machine. The simplicity of this method "of applying power lends smoothness of operation and flexibility of control. Certain types of machines require a variety of cutting speeds or feeds, changeable during operation. Presses, resistance welding machines, andthe like require sequential operation ofdifferent sizes of pistons at perhaps different pressures or speed of travel. shepers, planets, grinders, etc), require rapid approach to the work, slower movement over the work, and rapid return. All of these examples requi'res'equential operation clone or more parts with time. A- particular object of my present inven tion is to provide a control system providing sequential operation withtime; andau'apt'eu to a wide variety of machines; r V

The use of oil as a hydraulic medium provides smooth, vibrationlessaction tha'tis little affected by lead variations, having lubricating value and aminimum of compressibility or corrosionefie'ct. However, oil is'subject to change in viscositywith temperature so that an oil having proper vis= cosity at operating temperature; maythickeffx cessivel-y whenthe machine isnot used. Acha'rrging viscosity as the machine warms up may result in a wide variation'in speed of work or tool travel and may'require a continual readjustment of what was intended to'be an automatic ma-" chine or operation. change in the character'- istics of a hydraulic fluid is'particularly unclesirable in connection with the control for power cylinders; such as pilot valves and the like, In my present invention I desirably utilize oil" as a medium in power cylinders, but use air through out the control system for such power cylinders. I thus utilize a practically incompressible fluid in the locations where viscosity changes with temperature are of'minimum effect; and utilize a fluid which is insensitive to viscosity change with temperature the "control system where vol-me rate, s eed, direction and the like or "the power'pistons are established.

I ve chosen "as 'a preferred embodiment, to illustrate and"describe my invention as appliedto a res stance Welding machine, although broadly speak-mg, it is adaptable-to a wid r/anew of mach ine'sand operations; Ido not, therefore; desire tobe limited to my preferred embodiment.

In the drawings:

Fig. l-jdiagra-rnmatical'ly illustrates the spell: cation f my invention to a resistance welding ac n l l is. illustrates modification "of Fig. 1.

Fi s.' 3, 4', 5 and 6 diagrammatically lustrate d ifier'ent-cam arrangements for use ifn Fig. 1.

Fig, 7 is amodification of a part r Fig.1,

Referring now particular to Fig. 1, I illus tra'te ther' a resistance welding machine 1 having a stationary part 2.7 A movable portion 3 is positionable along ways 4 through the agency of a hydraulic motor 5 having apiston rod 6'. Inasmuch aswelding machines of this general type are well known it seems unnecessary to go into greater detail as to "construction of the ma chine I; It also appears unne'cessary to illustrate 0i d's ibe" Well lihowfielctrical Circuits and mechanisms for such a machine. I

As simple examp e I indicate that the chine I is desirably butt-welding together two pieces of tubing 1 and a. The tubing 1 is here by jaws of other means jon the'mova'bl'e portion 3 whilethe tubing fl'is h'el'd' fixedly in the pertion 2. When th'e'movableportion 3 is advances tOW-a'fd the stationary fibrtioli 2 the tubing. 1: preaches the tubing 8 and evehtuallyc'oi'i'ta'cts"it, Upon cbl'ltabt the electrical c iICllit is 'cd hffplelled, the temperature of the contact area is elevated, and awem of the'piec'es a is accomplished.

In such awelding operation it has been detertiv'ly smooth or uniform approach or the part" If the parts contact too slowly or 1 to the part 8 is accomplished; followed by a varying rate of pressure between the parts as the weld is accomplished. Different types and sizes of parts to be butt-welded or flash-welded may require a different gradation of movement or pressure between the parts and the accomplishment of such control of movement of the portion 3 of the machine forms a particular feature of my present invention.

In order that the forward movement of the piston rod 6 may bear a definite relation to time I control the passage of hydraulic fluid to or from the servo-motor 5 in accordance with the dictates of a time driven template 9 slidably mounted and positioned transversely (in the drawing) of the machine I through the agency of a rack l and pinion H. The pinion H is driven through any convenient ear reduction means l2 by an electric motor l3 adapted to be reversed as to rotation by means of a double-pole double-throw switch I 4.

For control of the servo-motor 5 I provide a tracer mechanism l5 supported by the movable portion 3 through a bracket [6 and having a feeler arm or tracer arm I! adapted to engage the contact surface [8 of the template 9. Thetracer assembly I5, I? may take the form disclosed and claimed in my copending application Serial No. 524,705, entitled Control system. In general I may say that the tracer mechanism comprises a valve adapted to bleed a pressure fluid to the atmosphere. In the particular embodiment being described I supply the body [5 with compressed air through a pipe I 9 at the discharge side of a restricting orifice 29 to which air is supplied at uniform pressure from a pressure regulator 2 I. It will be apparent that the pressure of the air in the pipe i9 will depend upon the rate of bleed to the atmosphere of air through the tracer mechanism [5. Such pressure is indicated upon a gage 22 and bears a definite relation to the deflection of the feeler arm I! relativ to the body l5.

Such air under pressure is eifective upon the bellows 23 of a variable fluid resistance 24. I show an oil pump 25 driven by a motor 26 and drawing its supply of oil from a sump 21.

In connection with the servo-motor 5 and adjustable fluid resistance 24 I provide switching valves 23 and 29 arranged to be moved together to either a normal or a rapid traverse position of operation. The valves 28 and 29 are shown in Fig. l in the normal operating position. Oil under pressure from the pump 25 is forced through a pipe 39, the valve 29, and a pipe 31 to one end of a servo-motor 5. Oil from the other end of the motor passes through a pipe 32. the valve 29, the valve 28, a pipe 33, the adjustable fluid resistance 24 and a pipe 34 to the sump 21. Regulation of the variable resistance 24 determines the rate of flow of oil through the pipe 32, and consequently the rat of travel of the piston rod 6 toward the portion 2 of the machine I. Thus the rate of approach of the work 1 toward the work 8 is controlled by the rate of passage of oil through the resistance 24 to the sump 21.

In Fig. 2 I show the passage relation of switching valves 28, 29 for a rapid return of the piston rod 6 upwardly in the drawing. That is for a rapid return of the portion 3 to the beginning of its working travel. Oil from the pump 25 passes directly through the pipe 30, the valve 29, and the pipe 32; while oil from th upper end of the cylinder 5 passes directly through the pipe 3|, the valve 29, the valve 28, and pipe 34 to the sump 21. Thus on the rapid return of the piston rod 9 upwardly in the drawing there is no throttling of its speed of travel by the variable resistance 24, and thus the portion 3 is traversed to the beginning of its working stroke at maximum speed.

It will be appreciated that th template 9, as well as the motor l3, are individually provided with the necessary travel limits or limit switches so that the template 9 may be positioned between definite limits of travel smoothly at uniform speed determined by the gear ratio [2 between the motor l3 and pinion ll. Upon reaching either extreme of travel motor I3 is stopped and travel in the reverse direction may be accomplished by throwing the switch M.

Preferably the control for the welding circuit as well as the switch I4 and valves 23, 29 are grouped conveniently to the operator. These various controls may b interlocked so that the advancing and retracting operation of the portion 3 is definitely tied to the welding circuit controls.

At the beginning of a cycle of operation the portion 3 is in its retracted position (upwardly on the drawing) and the template 9 is at its furthermost travel toward theright. The work pieces 7, 8 are fixed to the portions 3, 2 respectively. The valves 28, 29 are placed in the position shown in Fig. l and the switch I4 is closed to provide rotation of the motor I3 such that the template 9 moves toward the left in the drawing. According to the shape of the contact edge l8 of the template 9 the piston rod 6, portion 3, and work I move toward the work 8. If the surface I8 is a straight line inclined to a line normal to the axis of the machine I, then there will be a deflection of the feeler ll relative to the body l5 determined by the slope of Hi and a uniform rate of travel of the work 1 toward the work 8. In Fig. 1 the surface [8, is shown as having a rapidly increasing drop-off so that the travel of the work 1 toward the work 8, or the pressure applied between the work I and 8, is at an increasing rate with time as represented by rotation of th pinion II.

It is apparent that through the mechanism and system described I may readily control the rate of approach of the work 7 toward the work 8 or the rate of applying pressure'between the two parts during the welding operation. By properly shaping the surface I8 of the template 9 I may predetermine such rate of movement or rate of application of pressure.

In Fig. 3 I show a template 9 having a contact surface I 8 embodying a sequence of movement as follows: A dwell for a portion of the cycle, a sudden rapid advance, a dwelhand finally an advance at an increasingly rapid rate of speed.

In Fig. 4 I indicate a jet nozzle 35 on the pipe I9 directing a discharge of air directly against th contact surface l8 of the template 9. Here again (as in Fig. 1) the back pressure created in the pipe [9 is used to control the variable fluid resistance 24. The rate of discharge of air from the pipe I9 through the nozzle 35 to the atmosphere is dependent upon the approach or recession of the surface l8 to the end of the nozzle 35.

In Fig. 5 I indicate that the surface l8 may be wrapped around a cylinder 36, thus permitting a continuous rotation of the contact surface l8 in a single direction without the necessity of back traveling to a starting point as in Fig. 1.

The drum 36 may be rotated at a uniform speed by a synchronous motor or other means" representative-or time. The contact surface "48 may beef the type shown or may comprise a groove or ridge in the surface of the cylinder 36.

- In Fig. 6" a disc-31 may have a raised cam contact surface [8. Here again the assembly 31, I8 is to'be rotated continuously at a uniform speed" by a synchronous motor or other time device.

In F'ig. 7 I indicate that the template 9' may be positioned by a servo-motor 38 through the agency of hydraulic means such as oil, compressed air, cr'the like. Provisions for uniform movement of'the-piston 39- may include hydraulic bleed valve or adjustable orifice admission of pressure at a uniform rate against the piston 39 aswell as valve means for rapid return of the piston to the beginning of its controlling stroke. Certain features of such a timer, actuated through hydraulic or pneumatic means, are disclosed in the copending application of Clarence Johnson, Serial No. 542,149, entitled Control systems.

It will be apparent that the design and shape of'the template 9 may incorporate a sequence of timing or of operation including the positioning of fluid control valves, the regulation of speeds, the starting and stopping of operation, and the like. It will also be evident that the template 9 may be physically moved or may be rotated and that its rate of movement may be regulated or predetermined. Preferably the movement of the template 9 (regardless of its shape or form) is accomplished by a time element such as clockwork, synchronous motor, or the like, and is representative of a time function.

Thus in general I contemplate the positioning of members, or the direction of operations, in accordance with the dictates of a time controlled pattern or sequence.

It will be apparent that while I have chosen to illustrate and describe a preferred embodiment of. my invention as incorporated in a resistance welding machine nevertheless the invention is applicable to a wide variety of machines and/or operation.

What I claim as new, and desire to secure by Letters Patent of the'United States, is:

1. In a control system for a resistance welding machine ofthe type having means to control the speed of approach and subsequent pressure of engagement between a plurality of work pieces to be welded by the resistance to passage of electricity through their area of contact, and including a plurality of work holding portions of the machine arranged for relative movement to bring the'work pieces into engagement and to apply welding pressure between the work pieces, a hydraulic piston for relatively moving said portions, and means supplying a hydraulic fluid under pressure to the side of the piston producing relative approach of the work pieces and pressure between the work pieces upon contact thereof, the improvement therewith of pneumatic actuated means regulating release of fluid pressure from the other side of said piston to control the rate of travel of the piston and the rate of application of pressure upon contact of the work pieces, and time controlled program means controlling said regulating means to produce a predetermined rate of approach of the work pieces with time and thereafter a predetermined rate of applied pressure of the work pieces upon each other during the welding operation.

2. The combination of claim l wherein' said regulating means comprises an adjustable fluid resistance, and a fluid pressure control couple positioning said fluid resistance.

3. The combination of claim 1 wherein said regulating means comprises an adjustable fluid resistance, a fluid pressure control couple for adjusting said fluid resistance, said couple comprising a two element bleed valve to atmosphere, one element positioned by and with said piston, and the other element positioned by the time controlled program means.

4. In a control system for a resistance welding machine of the type having means to control the speed of approach and subsequent pressure of engagement between a plurality of work pieces to be welded by the resistance to passage ofelectricity through their area of contact, including a plurality of work holding portions of the machine arranged for relative movement to bring the work pieces into engagement and to thereafter apply welding pressure between the work pieces, a hydraulic piston for relatively moving said portions, means supplying a hydraulic fluid under pressure to the side of the piston producing relative approach of the work pieces and pressure between the work pieces after contact thereof, the improvement therewith of an adjustable fluid resistance regulating release of fluid pressure from the other side of said piston to control the rate of travel of the piston and the rate of application of pressure upon contact of the work pieces, a control couple comprising a two element bleed valve to atmosphere establishing a fluid back pressure for adjusting said adjustable fluid resistance, one of the valve elements positioned by and with the piston representative of the relative position of the work piece, and a time driven program template representing desired sequential relative approach of the work pieces followed by relative applied pressure per increment of time over a predetermined operating cycle, the second element of said couple positioned by said template.

5. The combination of claim 4' wherein the template is positioned by a synchronous electric motor representative of uniform time rate.

6. The combination of claim 4 wherein the template is positioned by a hydraulic pressure'representative of uniform time rate.

7. The combination of claim'e including means to return said piston to the beginning of its travel following completion of an operating cycle.

8. In a metal working machine, in combination, means for relatively moving a plurality of portions of the machine to perform a work operation, and time driven program means for" controlling such movement in accordance with a predetermined sequence of rate of relative movement per increment of time in an operating cycle, said program means including a template formed to represent desired sequential relative movement of the portions per increment of time, and synchronous motor means for positioning the template.

9. In a metal working machine, in combination, means for relatively moving a, plurality of portions of the machine to perform a work operation, a program template controlling said means, a control couple having a portion positioned by the machine and a cooperating portion positioned by the'template, and time means for positioning said template.

10. The combination of claim 9 in which said control couple comprises a fluid jet discharging to atmosphere whereby a fluid back pressure is established for controlling the first named means.

11. In a metal working machine, in combination, hydraulic means for relatively positioning portions'of the machine, means for connecting said hydraulic means selectively to liquid supply means or to exhaust, pneumatic means controlling the flow of liquid relative to said hydraulic means, means for conducting a pressure fluid relative to said pneumatic means, and means operating on a predetermined time program for controlling the flow of pressure fluid through said fluid conducting means.

12. In a metal working machine, in combination, hydraulic means for relatively positioning portions of the machine, pneumatic means including a fluid jet feeler positioned by movement of a portion of the machine for controlling the hydraulic means, and time controlled program means regulating the pneumatic means, said time controlled program means including a uniformly driven pattern arranged to be scanned by said feeler as the portions of the machine are relatively positioned.

13. In a Welding machine having relatively movable parts arranged in cooperative relation, hydraulically operated means for relatively positioning said parts, pneumatic means for controlling the hydraulically operated means, a feeler carried by one part of the machine for regulating the pneumatic means, and a time controlled program template arranged to be scanned by the feeler during relative motion of the machine parts.

14. In a Welding machine having a stationary part, and a cooperating movable part, a source of hydraulic pressure fluid, a hydraulic motor for actuating said movable part, means for supplying hydraulic pressure fluid to one side of the motor and removing it from the other side at a selected rate, pneumatically operated means controlling the rate of removing the hydraulic fluid from the motor, and time controlled program means regulating the pneumatically operated means.

15. In a welding machine having a stationary part and a cooperating movable part, a hydraulic piston connected to said movable part, means for supplying hydraulic pressure fluid to one side of the piston and removing it from the other side at a variable rate, and means for varying the rate of removing the pressure fluid from the hydraulic piston, said means including a uniformly driven template and a feeler carried and positioned by the movable part of the machine and arranged to scan the template to produce a predetermined rate of approach of said parts and thereafter a predetermined rate of applied pressure to work pieces between said parts.

16. In a welding machine having a stationary part and a cooperating movable part, a hydraulic piston connected to said'movable part, means for supplying hydraulic pressure fluid to one side of the piston and removing it from the other side at a variable rate, and pneumatically operated means for varying the rate of removing the pressure fluid from the hydraulic piston, said pneumatically operated means including a movable template, a pneumatic jet feeler carried by the movable part of the'machine and arranged to scan said template, and a synchronous motor driving said template.

17. In a machine having a movable part actuatable by fluid for performing a work operation, in combination, means for conducting a fluid relative to said movable part for effecting movement thereof, means for controlling the flow of fluid through said conducting means in accordance 'with a predetermined sequence of rate of movement in an operating cycle, said controlling means including a cam element formed to represent the desired movement of said part, a-control element cooperating with said cam element, and means for moving one of said elements relative to the other.

18. In a machine having a movable part actuatable by fluid for performing a work operation, in combination, means for conducting a fluid relative to said movable part for effecting movement thereof, means for controlling the flow of fluid through said conducting means to effect a predetermined sequence of rate of movement in an operating cycle, said controlling means including a cam element formed to represent the desired movement of said part, a control element carried by said movable part and cooperating with said cam element, and means for moving said cam element relative to said control element.

FREDERICK A. BARNES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

